x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 228 insertions, 0 deletions

diff --git a/drivers/nvmem/lan9662-otpc.c b/drivers/nvmem/lan9662-otpc.c
new file mode 100644
index 000000000..62d1d6381
--- /dev/null
+++ b/drivers/nvmem/lan9662-otpc.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#define OTP_OTP_PWR_DN(t)			(t + 0x00)
+#define OTP_OTP_PWR_DN_OTP_PWRDN_N		BIT(0)
+#define OTP_OTP_ADDR_HI(t)			(t + 0x04)
+#define OTP_OTP_ADDR_LO(t)			(t + 0x08)
+#define OTP_OTP_PRGM_DATA(t)			(t + 0x10)
+#define OTP_OTP_PRGM_MODE(t)			(t + 0x14)
+#define OTP_OTP_PRGM_MODE_OTP_PGM_MODE_BYTE	BIT(0)
+#define OTP_OTP_RD_DATA(t)			(t + 0x18)
+#define OTP_OTP_FUNC_CMD(t)			(t + 0x20)
+#define OTP_OTP_FUNC_CMD_OTP_PROGRAM		BIT(1)
+#define OTP_OTP_FUNC_CMD_OTP_READ		BIT(0)
+#define OTP_OTP_CMD_GO(t)			(t + 0x28)
+#define OTP_OTP_CMD_GO_OTP_GO			BIT(0)
+#define OTP_OTP_PASS_FAIL(t)			(t + 0x2c)
+#define OTP_OTP_PASS_FAIL_OTP_READ_PROHIBITED	BIT(3)
+#define OTP_OTP_PASS_FAIL_OTP_WRITE_PROHIBITED	BIT(2)
+#define OTP_OTP_PASS_FAIL_OTP_FAIL		BIT(0)
+#define OTP_OTP_STATUS(t)			(t + 0x30)
+#define OTP_OTP_STATUS_OTP_CPUMPEN		BIT(1)
+#define OTP_OTP_STATUS_OTP_BUSY			BIT(0)
+
+#define OTP_SLEEP_US 10
+#define OTP_TIMEOUT_US 500000
+
+struct lan9662_otp {
+	struct device *dev;
+	void __iomem *base;
+};
+
+static int lan9662_otp_wait_flag_clear(void __iomem *reg, u32 flag)
+{
+	u32 val;
+
+	return readl_poll_timeout(reg, val, !(val & flag),
+				  OTP_SLEEP_US, OTP_TIMEOUT_US);
+}
+
+static int lan9662_otp_power(struct lan9662_otp *otp, bool up)
+{
+	void __iomem *pwrdn = OTP_OTP_PWR_DN(otp->base);
+
+	if (up) {
+		writel(readl(pwrdn) & ~OTP_OTP_PWR_DN_OTP_PWRDN_N, pwrdn);
+		if (lan9662_otp_wait_flag_clear(OTP_OTP_STATUS(otp->base),
+						OTP_OTP_STATUS_OTP_CPUMPEN))
+			return -ETIMEDOUT;
+	} else {
+		writel(readl(pwrdn) | OTP_OTP_PWR_DN_OTP_PWRDN_N, pwrdn);
+	}
+
+	return 0;
+}
+
+static int lan9662_otp_execute(struct lan9662_otp *otp)
+{
+	if (lan9662_otp_wait_flag_clear(OTP_OTP_CMD_GO(otp->base),
+					OTP_OTP_CMD_GO_OTP_GO))
+		return -ETIMEDOUT;
+
+	if (lan9662_otp_wait_flag_clear(OTP_OTP_STATUS(otp->base),
+					OTP_OTP_STATUS_OTP_BUSY))
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static void lan9662_otp_set_address(struct lan9662_otp *otp, u32 offset)
+{
+	writel(0xff & (offset >> 8), OTP_OTP_ADDR_HI(otp->base));
+	writel(0xff & offset, OTP_OTP_ADDR_LO(otp->base));
+}
+
+static int lan9662_otp_read_byte(struct lan9662_otp *otp, u32 offset, u8 *dst)
+{
+	u32 pass;
+	int rc;
+
+	lan9662_otp_set_address(otp, offset);
+	writel(OTP_OTP_FUNC_CMD_OTP_READ, OTP_OTP_FUNC_CMD(otp->base));
+	writel(OTP_OTP_CMD_GO_OTP_GO, OTP_OTP_CMD_GO(otp->base));
+	rc = lan9662_otp_execute(otp);
+	if (!rc) {
+		pass = readl(OTP_OTP_PASS_FAIL(otp->base));
+		if (pass & OTP_OTP_PASS_FAIL_OTP_READ_PROHIBITED)
+			return -EACCES;
+		*dst = (u8) readl(OTP_OTP_RD_DATA(otp->base));
+	}
+	return rc;
+}
+
+static int lan9662_otp_write_byte(struct lan9662_otp *otp, u32 offset, u8 data)
+{
+	u32 pass;
+	int rc;
+
+	lan9662_otp_set_address(otp, offset);
+	writel(OTP_OTP_PRGM_MODE_OTP_PGM_MODE_BYTE, OTP_OTP_PRGM_MODE(otp->base));
+	writel(data, OTP_OTP_PRGM_DATA(otp->base));
+	writel(OTP_OTP_FUNC_CMD_OTP_PROGRAM, OTP_OTP_FUNC_CMD(otp->base));
+	writel(OTP_OTP_CMD_GO_OTP_GO, OTP_OTP_CMD_GO(otp->base));
+
+	rc = lan9662_otp_execute(otp);
+	if (!rc) {
+		pass = readl(OTP_OTP_PASS_FAIL(otp->base));
+		if (pass & OTP_OTP_PASS_FAIL_OTP_WRITE_PROHIBITED)
+			return -EACCES;
+		if (pass & OTP_OTP_PASS_FAIL_OTP_FAIL)
+			return -EIO;
+	}
+	return rc;
+}
+
+static int lan9662_otp_read(void *context, unsigned int offset,
+			    void *_val, size_t bytes)
+{
+	struct lan9662_otp *otp = context;
+	u8 *val = _val;
+	uint8_t data;
+	int i, rc = 0;
+
+	lan9662_otp_power(otp, true);
+	for (i = 0; i < bytes; i++) {
+		rc = lan9662_otp_read_byte(otp, offset + i, &data);
+		if (rc < 0)
+			break;
+		*val++ = data;
+	}
+	lan9662_otp_power(otp, false);
+
+	return rc;
+}
+
+static int lan9662_otp_write(void *context, unsigned int offset,
+			     void *_val, size_t bytes)
+{
+	struct lan9662_otp *otp = context;
+	u8 *val = _val;
+	u8 data, newdata;
+	int i, rc = 0;
+
+	lan9662_otp_power(otp, true);
+	for (i = 0; i < bytes; i++) {
+		/* Skip zero bytes */
+		if (val[i]) {
+			rc = lan9662_otp_read_byte(otp, offset + i, &data);
+			if (rc < 0)
+				break;
+
+			newdata = data | val[i];
+			if (newdata == data)
+				continue;
+
+			rc = lan9662_otp_write_byte(otp, offset + i,
+						      newdata);
+			if (rc < 0)
+				break;
+		}
+	}
+	lan9662_otp_power(otp, false);
+
+	return rc;
+}
+
+static struct nvmem_config otp_config = {
+	.name = "lan9662-otp",
+	.stride = 1,
+	.word_size = 1,
+	.reg_read = lan9662_otp_read,
+	.reg_write = lan9662_otp_write,
+};
+
+static int lan9662_otp_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct nvmem_device *nvmem;
+	struct lan9662_otp *otp;
+
+	otp = devm_kzalloc(&pdev->dev, sizeof(*otp), GFP_KERNEL);
+	if (!otp)
+		return -ENOMEM;
+
+	otp->dev = dev;
+	otp->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(otp->base))
+		return PTR_ERR(otp->base);
+
+	otp_config.priv = otp;
+	otp_config.dev = dev;
+	otp_config.size = (uintptr_t) device_get_match_data(dev);
+
+	nvmem = devm_nvmem_register(dev, &otp_config);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id lan9662_otp_match[] = {
+	{
+		.compatible = "microchip,lan9662-otpc",
+		.data = (const void *) SZ_8K,
+	},
+	{
+		.compatible = "microchip,lan9691-otpc",
+		.data = (const void *) SZ_16K,
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, lan9662_otp_match);
+
+static struct platform_driver lan9662_otp_driver = {
+	.probe = lan9662_otp_probe,
+	.driver = {
+		.name = "lan9662-otp",
+		.of_match_table = lan9662_otp_match,
+	},
+};
+module_platform_driver(lan9662_otp_driver);
+
+MODULE_AUTHOR("Horatiu Vultur <horatiu.vultur@microchip.com>");
+MODULE_DESCRIPTION("lan9662 OTP driver");
+MODULE_LICENSE("GPL");